1. Field of the Invention
The present invention relates to a method and an apparatus for receiving digital broadcast signals, for example, digital satellite broadcast signals.
2. Description of the Related Art
As television broadcast systems using geostationary satellites, digital broadcast systems, as well as analog broadcast systems, are coming into use. In the digital broadcast system, signals representing a plurality of television programs compressed according to, for example, the Moving Picture Experts Group (MPEG) method, can be multiplexed onto a single carrier and then be provided.
In a digital broadcast receiving apparatus, a user selects a carrier including the multiplexed television broadcast program that the user would like to audio-visually observe. The selected carrier is then demodulated, thereby obtaining a transport stream in which compressed data representing a plurality of television broadcast programs are multiplexed.
The compressed data of the target television broadcast program is then extracted from the transport stream. The extracted compressed data is decompressed, and an analog output video signal and an analog output audio signal are formed from the decompressed digital data. Images and sound of the target television broadcast program are reproduced from the analog output video signal and the analog output audio signal, respectively.
The above type of digital broadcast receiving apparatus is provided with a digital interface. Through this interface, a transport stream in which compressed data representing a plurality of broadcast programs are multiplexed can be supplied to and recorded on, for example, a digital video tape recorder (hereinafter referred to as the xe2x80x9cDVTRxe2x80x9d). Also, the recorded transport stream can be supplied from the DVTR to the digital broadcast receiving apparatus, and a television broadcast program contained in the supplied transport stream can be audio-visually observed by using the digital broadcast receiving apparatus.
As discussed above, transport streams are supplied to and received from the digital interface of the digital broadcast receiving apparatus. Accordingly, it is impossible to record and reproduce broadcast program signals output through the digital interface by using only an apparatus that is not provided with a compression/decompression function compatible with a compression method used in digital broadcasting.
For example, it is now assumed that a broadcast program signal provided by digital broadcasting has been recorded on a video tape with a DVTR connected to a digital broadcast receiving apparatus installed in a living room. Such a signal cannot be reproduced by a DVTR installed in another room that is neither connected to a digital broadcast receiving apparatus nor provided with a compression/decompression function compatible with the digital broadcast data compression method.
As noted above, the digital interface of the digital broadcast receiving apparatus supplies and receives transport streams. Thus, signals compressed by the MPEG method that are normally used in broadcasts cannot be recorded on a recording medium through this digital interface. For example, by using a recording/reproducing apparatus that uses as a recording medium a small magneto-optical disc, which is referred to as an MD, having a compression format different from the MPEG method (this apparatus will hereinafter be referred to as a xe2x80x9cMD unitxe2x80x9d), it is not possible to record on the MD only digital audio signals of a target music program or an education program concerning, for example, English conversation.
As described above, in most cases, the transport streams transmitted and received through the digital interface of a digital broadcast receiving apparatus cannot be utilized without the digital broadcast receiving apparatus. Accordingly, it is not possible to record or reproduce only a target broadcast program on or from a recording medium by using various digital external units, such as a DVTR and an MD unit.
The present invention provides a method and an apparatus for receiving digital broadcasts, in which broadcast program signals provided by a digital broadcast system can be supplied to various types of digital external units and be more effectively utilized.
According to one aspect of the present invention, there is provided a digital broadcast receiving apparatus comprising broadcast program extraction means for extracting compressed data including a broadcast program selected and specified by a user. Decompression means decompresses the compressed data extracted by the broadcast program extraction means and outputs decompressed data. Digital interface means receives the compressed data extracted by the broadcast program extraction means and the decompressed data from the decompression means, and outputs each of the compressed data and the decompressed data to a digital external unit. Control means controls, based on an instruction from the user, the selection of an output of the compressed data extracted by the broadcast program extraction means or an output of the decompressed data from the decompression means to the digital external unit from the digital interface means.
This makes it possible to receive digital broadcasts in which data is compressed and to directly supply the compressed data of a target broadcast program to the digital external unit, or to supply the decompressed data of a target broadcast program to the digital external unit. Accordingly, it is possible to supply the decompressed data even to a digital external unit which is not provided with a decompression function compatible with the data compression method of digital broadcasting and to utilize the decompressed data by being recorded on a recording medium.
In the aforementioned digital broadcast receiving apparatus, the broadcast program extraction means may comprise a tuner for selecting a carrier component including the broadcast program selected and specified by the user, a front end unit for demodulating the carrier component selected by the tuner and for outputting a transport stream, and selected-program extraction means for extracting compressed data of the broadcast program selected and specified by the user from the transport stream output from the front end unit. The broadcast program extraction means may output the transport stream from the front end unit to the digital interface means and also outputs the compressed data of the broadcast program from the selected-program extraction means to the decompression means. The digital interface means may receive the transport stream from the front end unit and decompressed data from the decompression means and may output each of the transport stream and the decompressed data to the digital external unit. The control means may control, based on an instruction from the user, the selection of an output of the transport stream or the decompressed data to the digital external unit from the digital interface means.
The extracted broadcast program signal may be digital data which is compressed by, for example, the MPEG method. The digital data is then supplied to the decompression means and is decompressed, thereby reproducing the original digital data (decompressed data).
This makes it possible to supply to the digital external unit not only the transport stream in which a plurality of broadcast program signals are multiplexed, but also to supply to the digital external unit the decompressed data of a single broadcast program and to record it on a recording medium used in the digital external unit.
If the decompressed data of a single broadcast program is recorded on a recording medium with the digital external unit, an output audio signal can be formed with the digital external unit to audio-visually observe the target broadcast program without needing to input again the decompressed data into the digital broadcast receiving apparatus provided with the decompression means.
According to another aspect of the present invention, there is provided a digital broadcast receiving apparatus for receiving a mixture of broadcast program signals provided as non-compressed data and broadcast program signals provided as compressed data. The digital broadcast receiving apparatus comprises a tuner for selecting a carrier component including a signal of a broadcast program selected and specified by a user. A front end unit demodulates the carrier component selected by the tuner and outputs a transport stream. Selected-program extraction means extracts the non-compressed data or the compressed data of the broadcast program selected and specified by the user from the transport stream supplied from the front end unit. Digital interface means receives the transport stream from the front end unit and the non-compressed data extracted by the selected-program extraction means, and outputs each of the transport stream and the non-compressed data to a digital external unit. Control means controls, based on an instruction from the user, the selection of an output of the transport stream or the non-compressed data to the digital external unit from the digital interface means.
With this arrangement, a multi-program transport stream and non-compressed data of a single broadcast program can be supplied to the digital external unit according to an instruction from the user. That is, the non-compressed data can be utilized by being recorded on a recording medium used in the digital external unit. Unlike the transport stream, the non-compressed data is not required to be decompressed, and it is unnecessary to input the non-compressed data into the digital broadcast receiving apparatus again when being reproduced. It is thus possible to supply the non-compressed data provided by digital broadcasting to the digital external unit and to effectively utilize it by being recorded on a recording medium.
The aforementioned digital broadcast receiving apparatus may further comprise decompression means for decompressing, if the signal of the broadcast program extracted by the selected-program extraction means is compressed data, the compressed data, and for outputting decompressed data. The digital interface means may receive the transport stream from the front end unit, the non-compressed data from the selected-program extraction means, and the decompressed data from the decompression means, and may output each of the transport stream, the non-compressed data, and the decompressed data to the digital external unit. The control means may control, based on an instruction from the user, the selection of an output of the transport stream, the non-compressed data, or the decompressed data from the digital interface means.
With this arrangement, the multi-program transport stream, the non-compressed data, or the decompressed data can be supplied to the digital external unit according to an instruction from the user. In this case, the digital data to be supplied to the digital external unit can be exchanged in accordance with the type of digital external unit or the method for the use of data. This makes it possible to supply the non-compressed data and the decompressed data provided by digital broadcasting to the digital external unit and to effectively utilize them by being recorded on a recording medium. As a result, information provided by digital broadcasting can be employed more effectively.
In the aforementioned digital broadcast receiving apparatus, the compressed data may comprise data which is compressed by the MPEG method. The non-compressed data may comprise digital data compressed by a method other than the MPEG method.
According to still another aspect of the present invention, there is provided a digital broadcast receiving method comprising: a broadcast program extraction step of extracting compressed data including a broadcast program selected and specified by a user; a decompression step of decompressing the compressed data extracted in the broadcast program extraction step and outputting decompressed data; a digital interface step of outputting each of the compressed data extracted in the broadcast program extraction step and the decompressed data output from the decompression step to a digital external unit; and a control step of controlling, based on an instruction from the user, the selection of an output of the compressed data extracted in the broadcast program extraction step and the decompressed data output from the decompression step to the digital external unit from the digital interface step.
In the aforementioned digital broadcast receiving method, the broadcast program extraction step may comprise a carrier component selection step of selecting a carrier component including a signal of the broadcast program selected and specified by the user, a front end step of demodulating the carrier component selected in the carrier component selection step and outputting a transport stream, and a selected-program extraction step of extracting compressed data of the broadcast program selected and specified by the user from the transport stream output from the front end step. The broadcast program extraction step may output the transport stream to the digital interface step from the front end step, and may also output the compressed data of the broadcast program to the decompression step from the selected-program extraction step. The digital interface step may output each of the transport stream output from the front end step and the decompressed data from the decompression step to the digital external unit. The control step may control, based on an instruction from the user, the selection of an output of the transport stream or the decompressed data to the digital external unit from the digital interface step.
According to a further aspect of the present invention, there is provided a digital broadcast receiving method for receiving a mixture of broadcast program signals provided as non-compressed data and broadcast program signals provided as compressed data. The digital broadcast receiving method comprises: a carrier component selection step of selecting a carrier component including a signal of a broadcast program selected and specified by a user; a front end step of demodulating the carrier component selected in the carrier component selection step and outputting a transport stream; a selected-program extraction step of extracting the non-compressed data or the compressed data of the broadcast program selected and specified by the user from the transport stream output from the front end step; a digital interface step of receiving the transport stream from the front end step and the non-compressed data extracted in the selected-program extraction step and outputting each of the transport stream and the non-compressed data to a digital external unit; and a control step of controlling, based on an instruction from the user, the selection of an output of the transport stream or the non-compressed data to the digital external unit from the digital interface step.
The aforementioned digital broadcast receiving method may further comprise a decompression step of decompressing, if the signal of the broadcast program extracted in the broadcast program extraction step is compressed data, the compressed data, and outputting decompressed data. The digital interface step may output each of the transport stream from the front end step, the non-compressed data from the selected-program extraction step, and the decompressed data from the decompression step to the digital external unit. The control step may control, based on an instruction from the user, the selection of an output of the transport stream, the non-compressed data, or the decompressed data from the digital interface step.